Cold mix and cold laid bituminous paving mixture



Patented Apr. 30, 1935 PATENT OFFICE corn MIX AND com) LAID BITUMINOUSPAVIN G MIXTURE Charles M. Baskin, Montreal, Quebec, Canada assigner toStandard Oil Development Company, a corporation of Delaware No Drawing.Application June 27, 1933, Serial No. 677,852

4 Claims.

This invention relates to improvements in bituminous pavingmixturesandprocess of making same and refers particularly to a combination of an.asphaltic mama, priming oil and crushed stone.

The use and preparation of paving mixtures of powdered asphalt incombination with liquid or partially liquid priming oils and mineralaggreate are well known. Various methods are used of incorporatingpriming oil and asphalt, the basis of which is the balancing out ofquantities of priming oil to powdered asphalt, so that when the twocombine by slow solution under pressure, it results in an asphalt binderof required consistency. This invariably requires at least of liquidpriming oil and 50% of asphalt powder. If the priming oil is of very lowviscosity, say below 590 seconds at 122 F. Furol, it is impossible tohold it in the mixture without running out before it has had a chance tothicken by the addition of the powdered asphalt. Where paving mixturesare required with a considerable lower consistency final binder thanusual, the quantity of priming oil to powdered asphalt may be as high aswhich requires an extra high iscosity oil to be able to hold it on thestone. Where a high viscosity oil is used, a slight preheating of theaggregate is required to be able to effectively mix it with the oil orit requires the thickening of the oil by the introduction of a solidbinder portion exclusive of the powered asphalt.

The use of thin priming oils has been proposed where fines and/or sandare present but as the thin priming oil is a very rapid solvent for thepowdered asphalt which is added, the mixture thickens almost immediatelyto a point where it cannot be stored, trans-shipped and laid. Thisprocess, therefore, requires a very vfine balance between the twoproducts in regard to solvent power and very often results in mixturesthat do not completely amalgamate as it is very diflicult to maintain asubstantial coating of the thin priming oil on the crushed stoneaggregate due to its tendency to flow.

An object of this invention is to provide a process of producingbituminous paving materials containing the required amounts of mineralaggregate, priming oil and asphalt which may be prepared in its entiretyat one central plant.

Other objects of the invention are as follows:

To provide a process of producing asphaltic paving material which willallow mixing easily and will be mobile during spreading.

To provide a process of manufacturing bituminous paving materials in thecold, that is, at atmospheric temperatures.

Additional features of the invention will 'be apparent from thefollowingdescription:

Predetermined quantities of priming oil, powdered asphalt and mineralaggregate are taken. The priming oil is divided into two parts and onepart of the priming oil is mixed with all of the mineral aggregate.After mixing thoroughly to wet all of the mineral aggregate, all of thepowdered asphalt is added and the mixture is mixed further to uniformlyincorporate the powdered asphalt in the priming oil coating the mineralaggregate. The remaining part of the priming oil is then added and themixing continued until the priming oil is uniformly dispersed over thefirst coating of priming oil containing the powdered asphalt.

Alternatively the first part of the priming oil and powdered asphalt maybe added at the same time to the mineral aggregate by spraying the oiland powder upon the surfaces of mineral aggregate being mixed in amixer.

The priming oil used in this process is an oil of low viscosity, toseconds at 122 F. Furol, and may be prepared from cracking coil tarreduced to this viscosity. The mineral aggregate may be of eitherpredetermined grading or density or as it is found or produced atrandom. The asphalt used is one oxidized to to 220 F. melting pointthoughasphalts of higher melting points up to 350 F. may be used. Thetypes of asphalts found preferable are those produced from cracking coiltar bottoms, Mexican crudes and California crudes.

The mixture is prepared without the application of heat and may bestored, shipped and spread as desired; The mixture is mobile even at lowtemperatures and is amalgamated by application of pressure afterspreading in layers of the desired thickness.

The proportion of ingredients generally used is two parts of priming oilto one part of asphalt and the total amount of asphalt and priming oiladded to a mineral aggregate is from 4 to 10% depending on fineness andpenetration of the resulting paving mixture desired.

The advantages of this process are as follows:

Low viscosity priming oil may be used so as to obviate heating and to beable to utilize all types of mineral aggregate irrespective of finenessof particles or grading.

Highly mobile mixtures are prepared that can be handled at ordinarytemperatures or even extreme low temperatures such as freezing.

Priming oil that has a high solvent power for the powdered asphalt maybe used, as the presence of an external oil film insures mobility for amuch longer time. This obviates the failures and difiiculties that haveoccurred in using priming oils of retarded solubility.

Various changes and alternative procedures may be adopted within thescope of the appended claims, in which it is my intention to claim allnovelty inherent in the invention as broadly as the prior art permits.

1. Method of producing a cold mix and cold laid bituminous pavingmixture using priming oils and powdered hard asphalts as thickeners,which comprises mixing a mineral aggregate with a priming oil, mixingthe mineral aggregate and priming oil with powdered asphalt, and mixingthe mineral aggregate, priming oil and powdered asphalt with a secondquantity of priming oil.

2. Method of producing a cold mix and cold laid bituminous pavingmixture using priming oils and powdered hard asphalts as thickeners,which comprises mixing a priming'oilof a viscosity of to seconds at 122F. Furol with a mineral aggregate, mixing a powdered asphalt of to 350F. melting point with the mixture of mineral aggregate and priming oil,and mixing a second portion of the priming oil with the mixture ofmineral aggregate, powdered asphalt and first quantity of priming oil. V

3, Method of producing a cold mix and cold laid bituminous pavingmixture using priming oil and powdered hard asphalt as thickeners, whichcomprises mixing the powdered asphalt, mineral aggregate, one-half ofthe priming oil, and mixing the remaining half of the priming oil withthe mixture of powdered asphalt, mineral aggregate and one-half of thepriming oil.

4. Method of producing a cold mix and cold laid bituminous pavementusing priming oil and powdered asphalt as thickeners, which compriseswetting a mineral aggregate with a low viscosity priming oil, mixing themineral aggregate with powdered hard asphalt, and wetting the mixture ofmineral aggregate, priming oil and powdered hard asphalt with a secondcharge'of low viscosity priming oil.

CHARLES M. BASKIN.

